Renewable energy system for hydrogen production and carbon dioxide capture

ABSTRACT

The present invention is an integrated system for the production of hydrogen and the removal of carbon dioxide from the air or gas streams. The integrated system includes an energy source for generating electrical energy and a water source coupled to the energy source. The water source includes ionic electrolytes. The energy source supplies energy to the water source to electrolyze water to produce hydrogen gas, oxygen gas, acid and base. The carbon dioxide reacts with the base. In some embodiments, the energy source is a renewable energy source. The integrated system produces substantially no carbon dioxide and when combined with a renewable energy source, produces clean hydrogen fuel and reduces atmospheric carbon dioxide, resulting in carbon dioxide negative energy and manufacturing strategies.

This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 60/921,598, filed on Apr. 3, 2007, entitled A NOVEL ELECTROCHEMICAL METHOD FOR REMOVING CARBON DIOXIDE FROM GAS STREAMS AND SIMULTANEOUSLY GENERATING HYDROGEN GAS, which is herein incorporated by reference in its entirety.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-owned and co-pending application entitled ELECTROCHEMICAL APPARATUS TO GENERATE HYDROGEN AND SEQUESTER CARBON DIOXIDE, filed on the same day and assigned Ser. No. ______ and to co-owned and co-pending application entitled ELECTROCHEMICAL METHODS TO GENERATE HYDROGEN AND SEQUESTER CARBON DIOXIDE, filed on the same day and assigned Ser. No. ______, both of which are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to the fields of renewable hydrogen production and carbon dioxide capture and sequestration. More specifically, the present invention relates to an integrated system that uses renewable energy in combination with water electrolysis to generate renewable hydrogen and capture and sequester carbon dioxide.

BACKGROUND OF THE INVENTION

The electrochemical cleavage of water has traditionally been viewed as a method of producing hydrogen and oxygen gas. In traditional alkaline water electrolysis, two molecules of hydroxide base are produced and consumed for every molecule of hydrogen generated. One common method of producing hydroxide base uses the chloralkali process in which sodium chloride, rather than water, is electrolyzed. While effective, the chloralkali method generates abundant chlorine, a toxic by-product, and generates several tons of carbon dioxide pollution per ton of manufactured base when powered with electricity generated from fossil fuels.

SUMMARY OF THE INVENTION

In one aspect, the present invention is an integrated system for the production of hydrogen and the removal of carbon dioxide including an energy source and a water source. The energy source generates electrical energy. The water source is coupled to the energy source and includes ionic electrolytes. The energy source supplies energy to the water source to electrolyze water to produce oxygen gas, hydrogen gas, acid and base. The carbon dioxide reacts with the base. The integrated system produces substantially no carbon dioxide.

In another aspect, the present invention is a system for producing value-added products and removing carbon dioxide including a water electrolysis process and an energy source. The water electrolysis process produces hydrogen gas and a hydroxide base. The energy source supplies an electrical input to the water electrolysis process. The hydrogen gas is collected and supplements the energy source and the base removes atmospheric carbon dioxide. The system removes more atmospheric carbon dioxide than it produces.

In yet another aspect, the present invention is an integrated system for capturing and converting carbon dioxide to a value-added product. The integrated system includes a renewable energy source for generating electricity and a water electrolysis apparatus. The energy from the renewable energy source is supplied to the water electrolysis apparatus to produce hydrogen, oxygen, a base and an acid, which are sequestered. The atmosphere has an initial concentration of carbon dioxide prior to supplying energy from the renewable energy source to the water electrolysis apparatus. After supplying energy from the renewable energy source to the water electrolysis apparatus, the base produced reacts with the carbon dioxide from the atmosphere such that the atmosphere has a resulting concentration of carbon dioxide less than the initial concentration of carbon dioxide. The carbon dioxide is then converted to a value-added product.

In still another aspect, the present invention is a system for recovering carbon dioxide including a water electrolysis apparatus having an anode and a cathode and a renewable energy source coupled to the water electrolysis apparatus for providing electrical energy to the water electrolysis apparatus. The water electrolysis apparatus produces oxygen and aqueous acid at the anode and produces hydrogen and aqueous base at the cathode. The aqueous base produced by the water electrolysis apparatus is used to capture carbon dioxide. The system captures more carbon dioxide than the system produces and produces less than about 100 mg of chlorine per liter of electrolyte.

In another aspect, the present invention is an integrated water electrolysis system for the production of hydrogen, oxygen, acid and base. The system includes an aqueous electrolyte solution, an electrical source, an anode and anode region and a cathode and cathode region. The anode and anode reaction region generate between about 100 and about 10,000,000 times more hydronium ions than are initially present in the electrolyte solution and the cathode and cathode reaction region generate between about 100 and about 10,000,000 times more hydroxide ions than are initially present in the electrolyte solution. The carbon dioxide reacts with the hydroxide ions to form carbonate or bicarbonate. The integrated electrolysis system produces substantially no carbon dioxide.

These and other aspects, processes and features of the invention will become more fully apparent when the following detailed description is read with the accompanying figures and examples. However, both the foregoing summary of the invention and the following detailed description of it represent one potential embodiment, and are not restrictive of the invention or other alternate embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an integrated water electrolysis system, according to one embodiment.

FIG. 2 is a schematic view of a water electrolysis device of the integrated water electrolysis system of FIG. 1, according to one embodiment.

FIG. 3 is a schematic view of an alternative embodiment of the water electrolysis device of FIG. 2, according to one embodiment.

FIG. 4 is a schematic view of an alternative embodiment of the water electrolysis device of FIG. 2, according to one embodiment.

FIG. 5 is a schematic diagram of value-added products that may be processed from the integrated water electrolysis system of FIG. 1.

FIG. 6 is a schematic diagram of a water electrolysis apparatus of the integrated water electrolysis system of FIG. 1.

While the invention is amenable to various modifications and alternative forms, some embodiments have been shown by way of example in the drawings and are described in detail below. As alluded to above, the intention, however, is not to limit the invention by those examples. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram of an integrated water electrolysis system 10 for generating renewable hydrogen and capturing carbon dioxide (CO₂), according to one embodiment. The integrated water electrolysis system 10 includes an electrical energy source 12, a renewable energy source 14, an electrolysis cell 16 including a cathode region 18 and a cathode 18 a, an anode region 20 and anode 20 a, an aqueous electrolyte source 22 housing an aqueous electrolyte solution 22 a, a hydrogen collection and storage reservoir 24, an oxygen collection and storage reservoir 26, a base collection and storage reservoir 28, an acid collection and storage reservoir 30, a first carbon dioxide capture apparatus 32 connected to the base collection and storage reservoir 28, a second carbon dioxide capture apparatus 34 connected indirectly to the acid collection and storage reservoir 30, a carbon dioxide product system 36 and a fuel cell 38. The integrated water electrolysis system 10 and its components produce hydrogen, oxygen, acid and base through water electrolysis, followed by subsequent processing of one or more of these products to capture carbon dioxide as carbonate salt, bicarbonate salt or mineral carbonates. Using the base produced by the integrated water electrolysis system 10 to capture carbon dioxide, renewable hydrogen is generated as a carbon dioxide negative rather than carbon dioxide neutral fuel and can be used as a large-scale application for reducing global carbon dioxide pollution. When combined with renewable or non-carbon dioxide producing energy sources, the integrated water electrolysis system 10 creates carbon dioxide negative energy strategies for producing clean hydrogen fuel and reducing carbon dioxide. The phrase “carbon dioxide negative” refers to the net overall reduction of carbon dioxide in the atmosphere or a gas stream. Thus, in stating that the integrated water electrolysis system 10 is carbon dioxide negative, it is meant that the integrated water electrolysis system 10 removes substantially more carbon dioxide than it produces. In addition, unlike traditional methods of manufacturing hydroxide base, no substantial carbon dioxide or chlorine gas is produced.

The electrical energy source 12 is a direct current (DC) electrical source and is coupled to the renewable energy source 14. The electrical energy source 12 and the renewable energy source 14 supply electricity to the electrolysis cell 16. The DC electricity is used at a predetermined and sufficient voltage to electrolyze water in the electrolysis cell 16 to charge the cathode region 18 and anode region 20 to power the electrolysis cell 16.

The renewable energy source 14 may be any renewable form of energy, such as wind, solar, hydroelectric, geothermal, oceanic, wave, tidal and fuel cells using renewable hydrogen. These renewable energy sources do not generate carbon dioxide. For example, wind acting upon a wind turbine can be used to generate direct current electricity. Other energy sources that may generate carbon dioxide may also be used to provide energy to the electrical energy source including biofuel, biomass, coal, methane and the like. According to one embodiment, nuclear energy may also be used to provide energy to the integrated water electrolysis system 10.

When powered by renewable energy, the integrated water electrolysis system 10 operates in an overall carbon dioxide negative fashion, removing net carbon dioxide from the air or gas streams and converting it to a variety of value-added products. Nuclear energy is an alternate source of electricity, and also allows carbon dioxide negative operation. Electricity from fossil fuel burning is another alternative, but does not currently allow carbon dioxide negative operation. With improvements in efficiency of the apparatus or the process of electricity generation, fossil fuel electricity would also allow a carbon dioxide negative operation of the apparatus.

In one embodiment, the energy generated by the renewable energy source 14 may be used to supplement the electrical energy source 12. In an alternative embodiment, the energy generated by the electrical energy source 12 may be used to supplement the renewable energy source 14. Excess electricity can be stored in a battery, converted by an inverter to alternating current for usage by the grid, or converted to hydrogen as an energy storage medium.

The electrical energy source 12 and the renewable energy source 14 supply a sufficient amount of electricity to initiate water electrolysis and electrolyze the aqueous electrolyte solution at the electrolysis cell 16. In one embodiment, a minimal voltage greater than about 1.2 V is applied to the electrolysis cell 16 to initiate and maintain electrolysis. According to other embodiments, the predetermined voltage supplied to the electrolysis cell 16 ranges from about 1.2 volts to about 10.0 volts. Application of a higher voltage can increase the rate of the reaction, with a penalty in energy efficiency.

The aqueous electrolyte solution housed in the aqueous electrolyte source 22 includes a concentrated aqueous electrolyte solution, such as a sodium, potassium, calcium, or magnesium sulfate, nitrate, or carbonate solution. According to various embodiments, the aqueous electrolyte includes an alkali salt. The alkali salt is a salt of the groups 1(IA) or 2(IIA) of the periodic table. Exemplary electrolytes suitable for use with the present invention include, but are not limited to, the following: sodium sulfate, potassium sulfate, calcium sulfate, magnesium sulfate, sodium nitrate, potassium nitrate, sodium bicarbonate, sodium carbonate, potassium bicarbonate, or potassium carbonate. Other suitable electrolyte solutions include sea water and aqueous sea salt solutions. In one embodiment, the aqueous electrolyte solution contains substantially no chloride such that the electrolysis cell 16 and/or integrated water electrolysis system 10, produce essentially no chlorine gas. In one embodiment, the integrated water electrolysis system 10 produces less than about 100 milligrams of chlorine per liter of electrolyte, particularly less than about 10 milligrams of chlorine per liter of electrolyte, and more particularly less than about 1 milligrams of chlorine per liter of electrolyte.

According to one exemplary embodiment of the present invention, the aqueous electrolyte solution is a saturated solution of sodium sulfate prepared by adding an excess of sodium sulfate to about 1000 liters of clean distilled water placed in a 1200 liter electrolyte processing and storage reservoir. The solution is maintained at about 30 degrees Celsius (° C.) while being mechanically mixed overnight. The resultant solution is filtered and then pumped into the electrolysis cell 16 using a pump or gravity feed.

The electrical energy supplied to the aqueous electrolyte solution in the electrolytic cell 16 causes electrochemical cleavage of the water to produce hydrogen, oxygen, base and acid. The hydrogen and base are generated at the cathode region 18 and oxygen and acid are generated at the anode region 20. The rising gases within the solution cause dynamic fluid convection, which is optimized by the electrolysis design. The convection flow of electrolyte within the cathode region 18 and anode region 20 minimizes the recombination of the newly generated base and acid typically experienced by traditional electrolysis cells. This allows each of the concentration of base and acid within the cathode region 18 and anode region 20 to increase to between about 100 and about 10,000,000 fold or more relative to its initial concentrations. Particularly, each of the concentration of base and acid within the cathode region 18 and anode region 20 increases to between about 10,000 and about 10,000,000 fold or more relative to its initial concentrations. More particularly, each of the concentration of base and acid within the cathode region 18 and anode region 20 increases to between about 100,000 and about 10,000,000 fold or more relative to its initial concentrations. Even more particularly, each of the concentration of base and acid within the cathode region 18 and anode region 20 increases to between about 1,000,000 and about 10,000,000 fold or more relative to its initial concentrations. Thus, in an aqueous electrolyte source 22 producing hydroxide base and hydronium acid, the concentration of hydroxide ions at the cathode region 18 is increased by more than one hundred fold and the concentration of hydronium ions at the anode region 20 is increased by more than one hundred fold. The integrated water electrolysis system 10 is thus capable of producing up to about 40 kilograms of sodium hydroxide or a molar equivalent amount of potassium hydroxide for every kilogram of hydrogen. In addition, according to some embodiments, the integrated water electrolysis system 10 is capable of producing up to about 49 kilograms of sulfuric acid for every kilogram of hydrogen.

Once concentrations of base and acid reach a minimal increase of one hundred fold relative to their initial electrolyte concentration, resulting in a pH difference between the cathode region 18 and anode region 20 of about four or more, fresh electrolyte is pumped from the aqueous electrolyte source 22 to the cathode region 18 and anode region 20. To equilibrate the volume of liquid in the cathode region 18 and anode region 20, resultant base and acid is removed from the cathode region 18 and anode region 20, respectively. Batchwise or continuous flow addition of electrolyte may be used to optimize production and operating conditions.

In one embodiment the fresh electrolyte is routed through a configuration of pipes, which branches into a “T” formation, just prior to entering the cathode region 18 and anode region 20. The current between the cathode region 18 and anode region 20 is conducted though the branched area of the electrolyte “T” configuration. The dynamic flow of the fresh electrolyte is in opposing directions as it enters the two electrolysis reaction regions. The electrolyte supply flow rate is adjusted to overcome ion migration due to the applied electric field, thereby eliminating recombination or mixing of contents from the anode and cathode reaction regions. The electrolyte supply flow rate can also be adjusted to increase, decrease or maintain the concentrations of the acid and base produced in their respective reaction regions.

FIG. 2 shows a schematic diagram of the electrolysis cell 16. Generally, the electrolysis cell 16 may be any apparatus that subjects an aqueous solution to an electric field of sufficient strength to reduce water at the cathode region 18 and oxidize water at the anode region 20. In one embodiment, the electrolysis cell 16 is a water electrolysis cell that converts aqueous electrolyte solution from the aqueous electrolyte source 22 to hydrogen, oxygen, base and acid. The water electrolysis cell 16 includes a parallel cathode 18 a and anode 20 a that contain closely spaced electrodes separated by a semi-permeable membrane 40. The semi-permeable membrane 40 reduces liquid mixing within the water electrolysis cell 16 but allows ion flow between the cathode 18 a and anode 20 a. This configuration maintains high electrical conductivity while minimizing loss of acid and base to recombination within the water electrolysis cell 16. Anion or cation specific membranes are used to limit salt contamination of the acid or base produced.

Fresh aqueous electrolyte solution flows in the same direction in both the cathode 18 a and anode 20 a, gradually becoming more basic in the cathode region 18 and more acidic in the anode region 20. Alternatively, fresh aqueous electrolyte solution may be introduced through one of the cathode 18 a and anode 20 a. In this case, selective ion flow across an anion or cation specific membrane 40 would ensure production of a highly pure acid or base, respectively. The water electrolysis cell 16 can be operated in parallel or counter-current flow modes. Counter-current flow minimizes chemical gradients formed across the semi-permeable membrane 40 and may reduce the energy required to create such gradients and produce highly concentrated acid and base. In a counter-current system, the highest concentrations of hydronium and hydroxide ions and their counter-ions are never located directly across the semi-permeable membrane 40 from one another, but instead reach maximum strength opposite incoming fresh aqueous electrolyte solution in the counter-cell. This design avoids the need to create a 13-14-unit pH gradients across the semi-permeable membrane 40, instead producing no higher than a 7-unit pH gradient between either strong acid and neutral electrolyte, or strong base and neutral electrolyte. Parallel current flow also has certain energy and design advantages.

FIG. 3 shows a schematic diagram of an alternative water electrolysis cell 16A. Water electrolysis cell 16A is a counter or parallel current flow three-chamber water electrolysis cell. A narrow central feed reservoir (such as electrolyte source 22) of fresh aqueous electrolyte solution is introduced between a first semi-permeable membrane 42 and a second semi-permeable membrane 44 that separate the cathode 18 a and anode 20 a. In a counter-current flow configuration, concentrated aqueous electrolyte solution enters the central feed reservoir at a first end of the water electrolytic cell 16A and concentrated base and acid exit the cathode 18 a and the anode 20 a, respectively. At a second end of the water electrolysis cell 16A, dilute base and acid enter the cathode 18 a and the anode 20 a, and water or dilute aqueous electrolyte solution exits the central feed reservoir. This design reduces salt contamination of base and acid produced and minimizes the chemical gradients formed across the permeable membranes 42 and 44. In some embodiments, the design may also be used to desalinate salt or seawater and produce hydrogen, oxygen, acid and base.

In practice, the cathode 18 a is initially filled with dilute base, and the anode 20 a is filled with dilute acid, maintaining electrical conductivity between the electrodes. Cations flow from the central feed reservoir through the first semi-permeable membrane 42 closest to the cathode 18 a, combining with hydroxide ions formed at the cathode 18 a to generate concentrated hydroxide base. Anions flow from the electrolyte solution source 22 through the second semi-permeable membrane 44 to the anode 20 a, combining with protons formed at the anode 20 a to produce concentrated acid. The semi-permeable membranes 42, 44 may be ion-selective (anion- or cation-specific) membranes, or may be passive barriers minimizing fluid flow, allowing passage of anions or cations in either direction. Regardless of membrane selectivity, such a 3-cell system can operate with parallel flow in all cells, or with countercurrent flow between the central feed reservoir and the cathode 18 a and anode 20 a on either side. The counter-current flow system minimizes chemical gradients across the membranes, because high concentrations of base and acid exit the cathode 18 a and anode 20 a opposite highly concentrated fresh electrolyte entering the central feed reservoir.

FIG. 4 is a schematic diagram of a stacked water electrolysis cell according to some embodiments of the present invention. The stacked porous electrodes may be used in some embodiments to maximize acid and base production. According to one embodiment, as shown in FIG. 4, the water electrolysis cell includes two or more porous anode-cathode pairs 18 a, 20 a aligned in a closely spaced parallel configuration. Semi-permeable or ion selective membrane(s) 52 are optionally included between the inner pair of electrodes. The membrane(s) 52 function to contain a narrow electrolyte feed reservoir located between the inner pair of porous anodes or cathodes. Fresh electrolyte flows from the reservoir outward, contacting the first pair of electrodes, where water oxidation occurs at the anode and water reduction occurs at the cathode. Thus, as water passes through each pair of electrodes it becomes increasingly acidic or basic. In one embodiment, the electrodes may consist of fine mesh screens, porous micro or nanosphere materials or thin plates with numerous flow channels penetrating the electrode. Varying DC voltages in the range of about 1.2 to about 10 Volts are supplied to these electrode pairs to maximize the production of acid in the anode chamber and base in the cathode chamber.

Referring back to FIG. 1, after water in the aqueous electrolyte solution has been electrolyzed to produce hydrogen, oxygen, base and acid, the products are sequestered and collected. The gases are routed from the cathode region 18 or anode region 20 to storage or flow systems designed to collect such gases. The low density of the gases relative to the aqueous electrolyte solution causes the gases to rise. The reaction conditions and structures are designed to direct this flow up and out of the cathode region 18 and anode region 20 and into adjacent integrated areas. The hydrogen, base, oxygen and acid are physically diverted for collection in the hydrogen collection and storage reservoir 24, the base collection and storage reservoir 28, the oxygen collection and storage reservoir 26 and the acid collection and storage reservoir 30, respectively.

The hydrogen and oxygen collected in the hydrogen collection and storage reservoir 24 and the oxygen collection and storage reservoir 26, respectively, may be used to generate electricity to power the integrated water electrolysis system 10, to supplement the electrical energy source 12 or to power a fuel cell (such as the fuel cell 38), furnace or engine to provide direct current electricity for water electrolysis. The hydrogen and/or oxygen may also be used to react with other products of the integrated water electrolysis system 10 to create more value-added products. Finally, the hydrogen and/or oxygen may be removed from the integrated water electrolysis system 10 as products to be sold or used as fuels or chemical feedstocks. Because the hydrogen produced with the integrated water electrolysis system 10 is generated through a carbon dioxide neutral or carbon dioxide negative process, the hydrogen offers a clean source of fuel.

The base generated by the water electrolysis cell 16 is sent to the base collection and storage reservoir 28 and is sold or used as a carbon dioxide neutral, highly purified commodity or chemically reacted with carbon dioxide gas to form carbonate or bicarbonate. When used to capture carbon dioxide, the carbon dioxide is captured as carbonate salt or bicarbonate salt. The carbon dioxide may be captured by reacting, sequestering, removing, transforming or chemically modifying gaseous carbon dioxide in the atmosphere or a gas stream. The gas stream may be flue gas, fermenter gas effluent, air, biogas, landfill methane, or any carbon dioxide-contaminated natural gas source. The carbonate salts may subsequently be processed to generate a variety of carbon-based products. For example, the carbonate salts may be concentrated, purified, enriched, chemically reacted, diverted, transformed, converted, evaporated, crystallized, precipitated, compressed, stored or isolated.

The reaction of the base with the carbon dioxide can be passive, without any physical effort to promote air-water-solid mixing. An example of a passive reaction includes an open-air reservoir filled with the base, or a solution containing the base, or a layer of solid hydroxide base exposed to the air or a gas stream. This reaction is spontaneous and can be driven by increased concentrations of base and carbon dioxide. The reaction can also proceed by active mechanisms involving the base or carbon dioxide. An example of an active reaction includes actively spraying, nebulizing, or dripping a basic solution in the presence of the carbon dioxide. In another example, carbon dioxide is actively reacted with the base by bubbling or forcing the gas stream through a column or reservoir of base generated by the water electrolysis cell 16. Combinations of active and passive carbon dioxide trapping systems are also envisioned. In both cases, sodium bicarbonate and sodium carbonate are formed by the integrated water electrolysis system 10. These reactions may take place within the integrated water electrolysis system 10 or may be removed from the integrated water electrolysis system 10 and transported to another site for capturing carbon dioxide from the atmosphere or a gas stream using the passive or active techniques previously described.

The acid produced by the water electrolysis cell 16 is routed to the acid collection and storage reservoir 30. The acid can be processed and removed from the system for sale as a commodity. The acid may be used to prepare certain mineral based carbon dioxide sequestering compounds, which are then used to capture carbon dioxide from the atmosphere or gas stream. The acid may also be used by the integrated system as a chemical reagent to create other value added products. The acid can be used to release the carbon dioxide from the carbonate or bicarbonate salts in a controlled manner to further process the released carbon dioxide into value-added products. These products may include, but are not limited to: carbon monoxide, formic acid, methanol, super-critical carbon dioxide, pressurized carbon dioxide, liquid carbon dioxide or solid carbon dioxide (dry ice).

When operated with renewable energy, the system produces base and/or acid that may be used to capture carbon dioxide from the atmosphere or a gas stream. In this mode, the overall integrated water electrolysis system 10 sequesters substantially more carbon dioxide than the integrated water electrolysis system 10 creates, resulting in a net negative carbon dioxide footprint. Any significant carbon dioxide trapping makes all of the products produced by the system carbon dioxide negative, particularly those carbon products synthesized or produced from atmospheric carbon dioxide.

FIG. 5 illustrates value-added products that may be processed from the carbon dioxide captured using the base and/or acid produced by the integrated water electrolysis system 10. The integrated water electrolysis system 10 processes the value-added products from the center of the diagram outward. As previously mentioned, base generated from water electrolysis is reacted with carbon dioxide to produce carbonate and bicarbonate salts. The carbonate and bicarbonate salts can in turn be converted to carbon monoxide by chemical reduction or reaction with hydrogen. The combination of carbon monoxide and hydrogen is Syngas, a critical cornerstone of synthetic organic chemistry. Through additional processing of these central products, a number of chemical building blocks, such as methane, urea, ethylene glycol, acetaldehyde, formaldehyde, limestone, acetic acid, methanol, formic acid, acetone and formamide can be formed. The value added chemical building blocks can be removed from the integrated water electrolysis system 10 for sale as products or remain in the integrated system for further processing to a second class of value-added products. These value-added end products are then removed from the integrated water electrolysis system 10 and sold, resulting in profitable conversion of carbon dioxide into carbon dioxide negative products. Simultaneous production of renewable hydrogen is subsidized by sale of these carbon products, creating a carbon dioxide negative energy strategy with potentially dramatic impacts on global warming.

The center circle of FIG. 5 depicts primary products that can be produced from the reaction of hydroxide base with carbon dioxide, or (in the case of carbon monoxide) by reaction of captured carbon dioxide with hydrogen. These chemical compounds include carbon dioxide, carbon monoxide, carbonate and bicarbonate, all of which can be easily inter-converted. They can be further processed to create standard chemical building blocks. In many cases, the hydrogen, oxygen, acid and base generated by the water electrolysis cell 16 can be used for this secondary processing. The building blocks can also be further processed within the integrated water electrolysis system 10 to make many valuable carbon based products, exemplary embodiments of which are shown in FIG. 5.

The commercial products manufactured from carbon dioxide trapped by the integrated water electrolysis system 10 represent carbon dioxide negative commodities, with the integrated water electrolysis system 10 producing an overall net decrease in gaseous carbon dioxide while creating value-added carbon products. Sale of these products may dramatically subsidize renewable hydrogen production, making clean hydrogen an inexpensive by-product of an industrial process focused on converting atmospheric carbon dioxide into valuable carbon-based products.

EXAMPLES

The present invention is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples were commercially obtained, or may be synthesized by conventional techniques.

Example 1

A water electrolysis cell, shown in FIG. 6, was constructed to demonstrate the feasibility of generating concentrated acid and base for carbon dioxide trapping. It consisted of a vertical central electrolyte feed tube about 2.5 centimeters (cm) in diameter, connected near its base to upward slanting anode and cathode tubes attached opposite one another. Wire, screen or flat, linear electrodes consisting of nickel, stainless steel or platinum were placed in the anode and cathode tubes near their points of attachment to the central tube. A concentrated, chloride-free electrolyte solution of aqueous sodium sulfate was introduced to the system via the central feed tube, creating an electrically conductive cell in which water was oxidized at the anode and reduced at the cathode. A small 15-watt solar panel was used to provide renewable electricity to the system.

When a DC current from the solar panel was applied to the system, hydrogen and hydroxide base were produced rapidly at the cathode while oxygen and acid formed at the anode. Hydrogen and oxygen gas flowed up the cathode and anode tubes, respectively, and were collected at the top. Acid and base accumulating in the anode and cathode tubes were collected via stopcock valves. Fresh electrolyte introduced to the central feed tube forced acid and base up the anode and cathode tubes, preventing them from recombining within the system. Within a few minutes of operation, the electrolyte in the anode cell had reached a pH of about 2, and in the cathode cell a pH of about 12, a differential of 10 pH units. Unlike the traditional chloralkali process for manufacturing hydroxide base, this renewable method of base production generated no chlorine or carbon dioxide. Sulfuric acid, a high demand commodity chemical, was produced instead of chlorine.

Base produced in the cathode cell began to trap atmospheric carbon dioxide immediately, a process that was greatly enhanced by maximizing air-water exposure. This was achieved by bubbling air or gas through the basic solution or by spraying base through a column of air or carbon dioxide containing gas.

A passive trapping approach also demonstrated clear carbon dioxide capture from the air. A small amount (20 g) of crystalline NaOH was spread in a thin layer on a glass plate exposed to the air. Over the first few days the hygroscopic NaOH absorbed significant water vapor from the air, becoming a soggy mass of crystals. During the course of the next two weeks these crystals gradually dried up and became opaque white in color, a visible change from the initial translucent NaOH crystals. The white crystals were a combination of sodium bicarbonate and sodium carbonate, formed from atmospheric carbon dioxide. Addition of an acid, vinegar, to these crystals resulted in vigorous bubbling as carbon dioxide was released back to the air.

Example 2

A second example used a 1-inch diameter glass tube sealed at the bottom with a porous glass frit. The frit allowed fluid and ion exchange between the inside and outside of the glass tube, creating an inner anode or cathode cell. Flat nickel or platinum electrodes were placed on opposite sides of the glass frit and attached to a 15 W DC photovoltaic panel or DC power supply. This system created a water electrolysis device that produced concentrated base inside the tube and concentrated acid outside the tube.

Depending on mode of operation, a pH differential of over 11 was quickly generated in this system; an acid-base concentration gradient of over 20 billion fold. The electrolyte inside the tube reached a pH of about 13, while across the frit, less than ¼ inch away, the electrolyte pH reached about 1.6. Vigorous production of hydrogen and oxygen were also observed.

Example 3

A third example included a two-chamber flow-through system constructed from machined plastic. A peristaltic pump was used to circulate electrolyte solution into the anode and cathode chambers, which were physically separated by a semi-permeable membrane or filter. Variable width plastic spacers were used to vary the gaps between the electrodes and the membrane. A nickel-copper alloy was initially used as electrode material. Hydrogen and oxygen were collected at valves at the top of the device, and acid and base were continually circulated past the electrodes until sufficient concentrations were reached. A variable output DC power source was used to generate voltages sufficient to electrolyze water.

pH differentials of over about 10 units were quickly achieved and maintained in this system. The nickel-copper electrodes proved susceptible to corrosion at certain voltages. Corrosion-resistant nickel, platinum, alloy or stainless steel electrodes would be more suitable for use in the reactive environments created within the water electrolysis system.

Overall, these experiments clearly demonstrate that water electrolysis can be used in an integrated strategy to produce renewable hydrogen and trap carbon dioxide from the air or gas streams. Given that renewable hydrogen produced by water electrolysis is already promoted as a clean alternative to fossil fuels, this combined renewable hydrogen/carbon dioxide capture technology represents a significant advance in reducing global carbon dioxide emissions. Unlike other carbon dioxide capture technologies, no chlorine or carbon dioxide are produced by this renewable process.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 

1. An integrated system for the production of hydrogen and the removal of carbon dioxide comprising: an energy source for generating electrical energy; and a water source coupled to the energy source, wherein the water source comprises ionic electrolytes, and wherein the energy source supplies energy to the water source to electrolyze water to produce oxygen gas, hydrogen gas, acid and base; wherein carbon dioxide reacts with the base; and wherein the integrated system produces substantially no carbon dioxide.
 2. The integrated system of claim 1, wherein the energy source is a renewable energy source.
 3. The integrated system of claim 2, wherein the hydrogen is used to generate renewable electricity to replace or supplement the renewable energy source.
 4. The integrated system of claim 2, wherein the renewable energy source is one of wind, solar, hydroelectric, geothermal, oceanic, wave or tidal.
 5. The integrated system of claim 1, wherein the energy source is one of biomass and biofuel.
 6. The integrated system of claim 1, wherein the carbon dioxide is captured from one of the atmosphere and a gas stream.
 7. The integrated system of claim 1, wherein the carbon dioxide is converted to a value-added product.
 8. The integrated system of claim 7, wherein the value-added product is one of methane, methanol, formic acid, urea, formaldehyde, carbon monoxide, formamide, acetone, acetic acid, supercritical carbon dioxide, limestone, acetaldehyde, ethylene glycol, ethanol, a bicarbonate salt or a carbonate salt.
 9. The integrated system of claim 7, wherein the value-added product is one of a building material, a plastic, a polymer, a resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a fiber, a foam, a film, paint, a carbon dioxide neutral fuel, a solvent, a stored source of carbon dioxide, a paving material, a filler for plastics, agricultural lime, baking soda or baking powder.
 10. The integrated system of claim 1, wherein the hydrogen is sent to the energy source.
 11. A system for producing value-added products, including renewable hydrogen, and removing carbon dioxide comprising: a water electrolysis process for producing hydrogen gas and a hydroxide base at a cathode and oxygen gas and acid at an anode; and an energy source for supplying an electrical input to the water electrolysis process; wherein the hydrogen gas is collected and supplements the energy source; wherein the base removes atmospheric carbon dioxide; and wherein the system removes more atmospheric carbon dioxide than it produces.
 12. The system of claim 11, wherein the energy source is a renewable energy source.
 13. The system of claim 12, wherein the renewable energy source is one of wind, solar, hydroelectric, geothermal, oceanic, wave or tidal.
 14. The system of claim 11, wherein the carbon dioxide is captured by reaction with the hydroxide base and is converted to at least one of carbonate salt or bicarbonate salt.
 15. The system of claim 11, wherein the value-added product is one of a building material, a plastic, a polymer, a resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a fiber, a foam, a film, paint, a carbon dioxide neutral fuel, a solvent, a stored source of carbon dioxide, a paving material, a filler for plastics, agricultural lime, baking soda or baking powder.
 16. The system of claim 11, wherein the hydrogen is used as fuel or chemical feedstock.
 17. An integrated system for capturing and converting carbon dioxide to a value-added product, the integrated system comprising: a renewable energy source for generating energy; and a water electrolysis apparatus, wherein the energy from the renewable energy source is supplied to the water electrolysis apparatus to produce hydrogen, oxygen, a base and an acid and wherein the hydrogen, the oxygen, the base and the acid are separately sequestered; wherein the atmosphere has an initial concentration of carbon dioxide prior to supplying energy from the renewable energy source to the water electrolysis apparatus; wherein after supplying energy from the renewable energy source to the water electrolysis apparatus, the base produced reacts with the carbon dioxide from the atmosphere such that the atmosphere has a resulting concentration of carbon dioxide less than the initial concentration of carbon dioxide; and wherein the carbon dioxide is converted to a value-added product.
 18. The integrated system of claim 17, wherein the renewable energy source is one of wind, solar, hydroelectric, geothermal, oceanic, wave or tidal.
 19. The integrated system of claim 17, wherein the value-added product is one of carbonate salt or bicarbonate salt.
 20. The integrated system of claim 19, wherein the acid is used to liberate the carbonate or bicarbonate as carbon dioxide for storage or for conversion to the value-added product.
 21. The integrated system of claim 17, wherein the value-added product is one of methane, methanol, formic acid, urea, formaldehyde, carbon monoxide, formamide, acetone, acetic acid, supercritical carbon dioxide, limestone, acetaldehyde, ethylene glycol, or ethanol.
 22. The integrated system of claim 17, wherein the oxygen and hydrogen are transported to and used at a fuel cell.
 24. The integrated system of claim 17, wherein the hydrogen is transported to the renewable energy source.
 24. A system for recovering carbon dioxide comprising: a water electrolysis apparatus having an anode and a cathode, wherein the water electrolysis apparatus produces oxygen and aqueous acid at the anode and produces hydrogen and aqueous base at the cathode; and a renewable energy source coupled to the water electrolysis apparatus for providing energy to the water electrolysis apparatus; wherein the aqueous base produced by the water electrolysis apparatus is used to capture carbon dioxide; wherein the system captures more carbon dioxide than the system produces; and wherein the system produces less than about 100 mg of chlorine per liter of electrolyte.
 25. The system of claim 24, wherein the system produces less than about 10 mg of chlorine per liter of electrolyte.
 26. The system of claim 25, wherein the system produces less than about 1 mg of chlorine per liter of electrolyte.
 27. The system of claim 24, wherein the carbon dioxide is converted to a value-added product.
 28. The system of claim 27, wherein the value-added product is one of carbonate salt and bicarbonate salt.
 30. The system of claim 27, wherein the value-added product is one of methane, methanol, formic acid, urea, formaldehyde, carbon monoxide, formamide, acetone, acetic acid, supercritical carbon dioxide, limestone, acetaldehyde, ethylene glycol, or ethanol.
 31. The system of claim 27, wherein the value-added product is one of a building material, a plastic, a polymer, a resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a fiber, a foam, a film, paint, a carbon dioxide neutral fuel, a solvent, a stored source of carbon dioxide, a paving material, a filler for plastics, agricultural lime, baking soda or baking powder.
 32. The system of claim 24, wherein the renewable energy source is one of wind, solar, hydroelectric, geothermal, oceanic, wave or tidal.
 33. The system of claim 24, wherein the carbon dioxide is captured from one of the atmosphere or a gas stream.
 34. The system of claim 33, wherein the system captures carbon dioxide from a gas stream, wherein the gas stream is one of a flue gas, fermenter gas effluent, air, biogas, landfill methane or carbon dioxide contaminated natural gas.
 35. The system of claim 24, wherein the energy source is one of biomass or biofuel.
 36. An integrated water electrolysis system for the production of hydrogen, oxygen, acid and base comprising: an aqueous electrolyte solution; an electrical source; an anode and anode reaction region comprising hydronium ions, wherein an operational concentration of the hydronium ions is between about 100 and about 10,000,000 times higher than an initial concentration of the hydronium ions; and a cathode and cathode reaction region comprising hydroxide ions, wherein an operational concentration of the hydroxide ions is between about 100 and about 10,000,000 times higher than an initial concentration of the hydroxide ions; wherein carbon dioxide reacts with the hydroxide ions to form carbonate or bicarbonate; and wherein the integrated water electrolysis system produces substantially no carbon dioxide.
 37. The system of claim 36, wherein the electrolyte solution comprises sodium or potassium sulfate at a sulfate concentration of greater than about 0.1 molar.
 38. The system of claim 36, wherein the base produced is one of sodium hydroxide or potassium hydroxide.
 39. The system of claim 38, wherein the integrated water electrolysis system produces greater than about 40 grams of sodium hydroxide or potassium hydroxide for every kilogram of hydrogen.
 40. The system of claim 36, wherein the acid produced is sulfuric acid.
 41. The system of claim 40, wherein the integrated water electrolysis system produces greater than about 49 grams of sulfuric acid for every kilogram of hydrogen.
 42. The system of claim 36, and further comprising a hydrogen fuel cell, wherein the hydrogen is sent to a hydrogen fuel cell to provide direct current electricity to the integrated water electrolysis system.
 43. The system of claim 36, wherein the integrated water electrolysis system removes more carbon dioxide from the atmosphere or a gas stream than it produces.
 44. The system of claim 36, wherein the carbonate or bicarbonate is converted to at least one of the group consisting of: methane, methanol, formic acid, urea, formaldehyde, carbon monoxide, formamide, acetone, acetic acid, supercritical carbon dioxide, limestone, acetaldehyde, ethylene glycol, or ethanol.
 45. The system of claim 36, wherein the carbonate or bicarbonate is converted to one of a building material, a plastic, a polymer, a resin, a fabric, a fertilizer, antifreeze, a lubricant, a buffer, a pesticide, a fiber, a foam, a film, paint, a carbon based fuel, a solvent, a stored source of carbon dioxide, a paving material, a filler for plastics, agricultural lime, baking soda or baking powder. 